With their hard beaks and expressionless faces, birds do not appear to respond to a delicious flavour or a bad odour as we do. This may partly explain why ornithologists have been slow to attribute taste and smell to them. We still know so little that there is huge potential for discovery here. But for now, it is another little-known sense – the mysterious ability to detect the Earth’s magnetic field – that excites most interest among researchers.

A matter of taste

Dogs often swallow their food so rapidly it seems they barely have time to taste anything, but as every dog owner knows, they are certainly not indifferent to taste. The same is true of birds.

Early evidence of a sophisticated gustatory sense in birds was found by John Weir, a bird-keeping colleague of Charles Darwin and Alfred Wallace. He noticed that, when given caterpillars of the ermine moth, his cage birds spat them out and shook their heads in disgust. At the time, though, Weir’s discovery of a sense of taste in birds was rather eclipsed by Wallace’s realisation that distasteful caterpillars often sport warning colours, and that the two traits evolved together as a signal to would-be predators.

Later investigators assumed that, like us, birds must have taste buds on the tongue. When they looked for these they found a puzzle, because they seemed to have too few to discriminate between palatable and distasteful foods. Then, in 1974, Herman Berkhoudt at the University of Leiden in the Netherlands discovered what

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